The present invention generally relates to a method for removing copper oxide from a copper surface, and more particularly, to such a process incorporated in a semiconductor manufacturing process.
Copper interconnects have now been generally established in semiconductor devices. A common problem encountered in the use of copper interconnects has been the formation of a copper oxide coat during semiconductor processing, such as after the step of chemical-mechanical polishing (CMP) of the semiconductor device. The residual copper oxide on the surface is highly undesirable because it reduces and degrades the adhesion, and hence, interconnect reliability, between the copper surface and a film subsequently deposited on the copper. The film deposited on the copper interconnects is typically a protective film or etch stop layer, such as SiN, SiC, or a nitrogen-doped silicon carbide layer (e.g., NBLOK™, or “SiCN”).
Because of the adverse effects of copper oxide on copper interconnects, a copper oxide removal step is generally included in semiconductor processing. In the conventional processing of semiconductors, copper oxide removal is accomplished by a plasma treatment step. However, the plasma treatment is particularly problematic in that it causes damage to the interlevel dielectric (ILD) material contained on the semiconductor device. The damage to the ILD material by plasma treatment can be particularly acute in the case of 32 nm and beyond processing technologies. Other methods of copper oxide removal include treating the oxidized copper layer with a strong acid, such as nitric acid. However, chemical treatments with a strong acid tend to cause damage, such as pitting, to the copper surface.
Accordingly, there are efforts to find a method for copper oxide removal that effectively removes the copper oxide layer while not adversely affecting the semiconductor device. It would be further desirable if such a method were readily integratable into existing semiconductor processing designs. It would also be desired for the method to be similar or lower in cost than existing copper oxide removal technologies.